The torus of gas and dust can block part of our view
Seyfert 2 galaxies:   Edge on view
       Only gas well above and below disk is visible
       See only “slow” gas narrow emission lines
Seyfert 1 galaxies:   Slightly tilted view
       Hot high velocity gas close to black hole is visible
       High velocities   broad emission lines
BL Lac objects:   Pole on view
       Looking right down the jet at central region
       Extremely bright – vary on time scales of hours
Quasars:     Very active AGN at large distances
       Can barely make out the galaxy surrounding them
       Were apparently more common in distant past